1. Field of the Invention
The present invention relates to a camera winding-up apparatus which uses a cartridge in which a film is housed in such a manner that it is wound around a cartridge spool and which winds up this film by a wind-up spool.
2. Related Background Art
A system having a cartridge different from a currently used 135-type film cartridge is disclosed in U.S. Pat. No. 4,832,275. In this film cartridge, at first the front end of a film is not exposed to outside of the cartridge. When a cartridge spool is rotated in the film feeding direction after it is loaded into a camera, the film is thrust out of the cartridge.
The inventor of the present invention has previously proposed a camera winding/rewinding apparatus, in which the above kind of film cartridge is loaded, in U.S. Ser. No. 599,830 (filed on Oct. 19, 1990).
FIG. 9 is a perspective view schematically showing this above apparatus.
In this apparatus, a spool 3a of a cartridge 3 is driven via a driving mechanism 2 and a wind-up spool 5 of a camera is driven via a driving mechanism 4 by one film feeding motor 1. The ratio of the gear of the driving mechanism 2 to that of driving mechanism 4 is set in such a manner that the feeding speed of a film 6 is slower than the peripheral speed of the wind-up spool 5. The film 6 is fed at a speed slower than the peripheral speed of the wind-up spool 5 during the initial winding-up, i.e., until the film 6 is wound around the wind-up spool 5 after it is fed from the cartridge 3. As a result, the film 6 is reliably wound around the wind-up spool 5. Since, even after the front end of the film 6 is wound around the wind-up spool 5, both spools 3a and 5 are driven at the same gear ratio, the film 6 is pulled out of the cartridge 3 by the wind-up spool 5, instead of it being thrust out of the cartridge 3 by the cartridge spool 3a.
In this film cartridge 3, the film 6 expands outwardly inside the cartridge 3 in response to the rotation of the cartridge spool 3a during the initial film feeding, and then comes out of the cartridge 3. That is, the film 6 is in a loosely wound state relative to the cartridge spool 3a. Even after the front end of the film 6 is wound around the wind-up spool 5 during the initial winding-up, the film 6 inside the cartridge 3 is in this loose state for some time. Each time one film frame is fed after photo-taking, the film 6 inside the cartridge 3 becomes gradually tighter. This is due to the fact that the ratio of the gear of the driving mechanism 2 to that of the driving mechanism 4 is set in such a manner that the feeding speed of the film 6 is slower than the peripheral speed of the wind-up spool 5.
When photo-taking and one-frame feeding is repeated following the above operation, the film 6 inside the cartridge 3 is completely tightly wound around the spool 3a. Thereafter, the cartridge spool 3a is not driven via the driving mechanism 2, but instead it is driven by the action of the film 6 being pulled out from the cartridge 3. The rotational speed of the cartridge spool 3a is faster than the speed at which it is driven via the driving mechanism 2, thus causing the rotational speed of each gear of the driving mechanism 2 to increase via a fork 7. As a result, a one-way clutch 8 inside the driving mechanism 2 is disconnected, thereby causing the difference between the rotation caused by the motor 1 and the rotation caused by the action of the film 6 being pulled out to be absorbed.
If a distinction is made between the time until a film is tightly wound around a cartridge spool when the film is being wound by such a winding/rewinding apparatus, which time is called "first-half winding period" and the time after it is tightly wound, which time is called "second-half winding period", the point in time at which these first and second half winding periods are switched changes due to the dimension of a cartridge, a gear ratio or the like. For example, in a 36-frame cartridge, such point in time is near the tenth or the 15th frame.
As described above, in the first-half winding period, the film 6 is pulled out of the cartridge 3 by the wind-up spool 5. Since the cartridge spool 3a driven by the motor 1 only attemps to loosely wind up the film 6 inside the cartridge 3, the load of the motor 1 for driving the cartridge spool 3a via the driving mechanism 2 is small.
On the other hand, in the second-half winding period, since the section from the one-way clutch 8 to the cartridge spool 3a is disconnected by the one-way clutch 8, the load for the driving mechanism 2 of the motor 1 becomes smaller. However, at this time, the section from the cartridge spool 3a to the one-way clutch 8 is driven by the film 6 tightly wound onto the cartridge spool 3a. This becomes a load for the motor 1 via the wind-up spool 5 and the driving mechanism 4.
As described above, when the load of the motor 1 during the first- and second-half winding periods is considered in its entirety, the load of the motor 1 during the second-half winding period is greater than that during the first-half winding period. An increase in the load of the motor in the middle of this winding causes its rotational speed to decrease. As a result, the film feeding speed decreases.
Particularly, when a power cell whose service life is near the end is used, even if it operates normally during the initial winding period because the load is light, the winding speed will decrease abnormally in the latter half period of the winding and there is a danger that the continuation of photo-taking will be impaired.
Therefore, if a film is wound by a conventional winding/rewinding apparatus, the operability and reliability of a camera is decreased. Further, when various photo-taking information is recorded on the film during winding, the information recording density varies due to an unstable winding speed. This presents the problem that the reliability of recorded information is diminished.
Although, in the above description, a case of a push-out cartridge/normal winding method is described, the present invention is not limited to such a case. The same can be said of general 135-type cartridges and a preliminary winding method.